After losing her temper with Jess and letting him know she doesn’t trust him one bit around her daughter, Lorelai tries to find out from Luke if there is anything going on between Jess and Rory. Luke says that Jess doesn’t confide in him, but he thinks it would be great if they got together, because Rory would be good for Jess.
Lorelai is much more concerned about whether Jess would be good for Rory, and she now knows that Luke may be her friend, but he is not her ally when it comes to keeping Jess and Rory apart. This is no doubt painful to learn, and it also means that her distrust and resentment towards Jess begins to spread to Luke. Again, this will lead to a major break between Lorelai and Luke later down the track.
Jess was brought in by the writers to drive a wedge between Lorelai and Luke and keep them apart, and their plan is working.
(Note that the canisters behind Luke read SUGAR CAFE!).